This chapter provides a comprehensive, evidence-based analysis of Attention-Deficit/Hyperactivity Disorder (ADHD) in pediatric populations. It opens with a precise clinical definition based on DSM-5 criteria, detailing the distinct manifestations of inattention, hyperactivity, and impulsivity. Incorporating recent global epidemiological data, the text highlights prevalence rates, gender disparities, and common psychiatric comorbidities that challenge academic and social development. The etiological framework maps a complex interplay of high genetic heritability (such as variants in dopamine regulation) alongside prenatal and postnatal environmental risk factors. Furthermore, it explores underlying neurobiological mechanisms, focusing on subcortical-cortical dysconnectivity within executive and motivational brain circuits. A central focus is placed on holistic, multimodal management. The chapter evaluates pharmacological options, positioning stimulants as the gold standard for symptom control, while critically reviewing non-pharmacological supportive therapies—including physical exercise, cognitive training, behavioral interventions, and neurofeedback. Finally, it highlights the expanding roles of nurses, particularly school nurses, as vital bridges in early identification, treatment monitoring, family-school collaboration, and the reduction of social stigma, ultimately aiming to maximize each child's potential.